tree68 oltmannd ...and by "really move" I don't mean higher track speeds. I mean less time stopped and going slow. So the train gets to its hold-out parking spot a little sooner...
oltmannd ...and by "really move" I don't mean higher track speeds. I mean less time stopped and going slow.
...and by "really move" I don't mean higher track speeds. I mean less time stopped and going slow.
So the train gets to its hold-out parking spot a little sooner...
Track conditions permitting, you could double restricted speed since ECP braking at lower speeds cuts stopping distance by more than half. (the higher the speed, the lower the advantage)
So, maybe that yard congestion goes away, too?
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
mvlandsw BaltACD When I was still working CSX was instructing Engineers that Dynamic Braking was their primary form of braking and the use of air brakes was a secondary braking tool. I can only believe in the past 7 years that the use of air brakes has been incresingly discouraged. ECP or not, if you aren't using air in the first place there is absolutely no advantage to ECP. Except in an emergency application where all the brakes would apply at once instead of serially, eliminating the problems caused by severe slack action. Still probably not economically justifiable.
BaltACD When I was still working CSX was instructing Engineers that Dynamic Braking was their primary form of braking and the use of air brakes was a secondary braking tool. I can only believe in the past 7 years that the use of air brakes has been incresingly discouraged. ECP or not, if you aren't using air in the first place there is absolutely no advantage to ECP.
When I was still working CSX was instructing Engineers that Dynamic Braking was their primary form of braking and the use of air brakes was a secondary braking tool. I can only believe in the past 7 years that the use of air brakes has been incresingly discouraged. ECP or not, if you aren't using air in the first place there is absolutely no advantage to ECP.
Except in an emergency application where all the brakes would apply at once instead of serially, eliminating the problems caused by severe slack action. Still probably not economically justifiable.
If you are only going to look at ECP for it's effect on braking on each individual train, you are 100% correct.
Overmod daveklepper A rapid sharp drop in train-line air pressure, that would execute an emergency stop by propagation of the pressure drop alone, must also activate the electrical\electronic emergency braking. It does already, on both systems. The immediate actuation of all emergency valves in the train simultaneously, rather than 'at the speed of sound in compressed air', is what produces the roughly 3% reduction in achieved stopping distance. I do not know whether providing an ECP emergency trip at each emergency valve, to be triggered when any valve in the train physically goes to emergency, or if the trainline pressure drops 'uncommanded' below a critical level, is part of current systems. A problem with it is that any sort of UDE instantly slams the train into full emergency without warning, but all the issues with brakes applying differently or slack condition still apply regardless of how quickly the valve modulates.
daveklepper A rapid sharp drop in train-line air pressure, that would execute an emergency stop by propagation of the pressure drop alone, must also activate the electrical\electronic emergency braking.
It does already, on both systems. The immediate actuation of all emergency valves in the train simultaneously, rather than 'at the speed of sound in compressed air', is what produces the roughly 3% reduction in achieved stopping distance.
I do not know whether providing an ECP emergency trip at each emergency valve, to be triggered when any valve in the train physically goes to emergency, or if the trainline pressure drops 'uncommanded' below a critical level, is part of current systems. A problem with it is that any sort of UDE instantly slams the train into full emergency without warning, but all the issues with brakes applying differently or slack condition still apply regardless of how quickly the valve modulates.
You're probably a lot less likely to pop cars off on curves due to long car/short car/empty/loaded disparities with ECP emergency application. But, that alone won't get you your ROI.
oltmanndTrack conditions permitting, you could double restricted speed since ECP braking at lower speeds cuts stopping distance by more than half. (the higher the speed, the lower the advantage)
Braking distance scales with the square of the speed, so halving the breaking distance would give about a 41% increase in speed.
CSX RobertBraking distance scales with the square of the speed, so halving the braking distance would give about a 41% increase in speed.
oltmanndSo, maybe that yard congestion goes away, too?
I hear a lot of stories from various sources (including here on the forum) about trains being held out miles from their destinations because there is "no room at the inn." ECP isn't going to cure that.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
oltmannd If you take PTC, ECP and DPU together you can have these things: 1. lighter freight cars with lower buff force requirement
If you take PTC, ECP and DPU together you can have these things:
1. lighter freight cars with lower buff force requirement
Maybe? I kind of doubt it. Are cars really designed for the purpose of survive emergency slack run-in? They're designed to handle normal in-train forces, many of which occur without the automatic brakes being engaged at all, and forces experienced during switching and coupling activities. For the structural elements of the car (as opposed to the draft gear), surviving over speed coupling events (i.e. 6+ MPH collisions) may be limiting factor.
2. eliminate time pumping air
In what context exactly? The reservoirs still have to be charged from the train line.
3. automated brake testing
This would have some benefits, but less than you might think. If every train origination and on-line pickup still requires someone to walk the train inspecting other features of the car (such as safety appliances), then automating the brake test has less value. If you can automate inspection of other features - which the industry has been working on for decades - that would help.
4. faster restricting speed
On the mainline, most contexts requiring restricted speed are either a.) solvable by the more-advanced train-control systems that are in the works, thanks to PTC, or b.) protecting a potential track defect such as a broken rail, where there is good reason to limit speeds anyways.
In yards, 80-90% of all tracks are limited to 10 MPH by turnout size and track condition. And many movements within the yard don't have air cut in except on a few cars on the head end. (If braking performance was limiting yard capacity, we could start by using more of the existing brakes.)
5. greatly reduced PU/SO times (see #2, #3)
Because why? See #2 and #3. For a setout in particular, I'm not seeing any savings. For a pickup, you still need to charge the air on the cars you're picking up, and you still need to do at least a minimal inspection to ensure they're all on the rail. Parking brakes that could be set and released from the head end - which is something that has been discussed on this forum - would be convenient. Like on-board sensors, those don't necessarily require ECP brakes, although IF the EC line is designed for it, this feature might be able to take advantage of it.
6. reduced derailment risk - onboard health monitoring.
This requires assuming many things that are unknown, such as:
A.) The EC line supplies power to these sensors and can make use of data from them
B.) On-board sensors can be developed that work reliably with acceptable installation and maintenance costs
C.) Such sensors do a better job of preventing derailments than wayside detectors + periodic car inspection - allowing for the fact that wayside detector technology is also continuing to improve while the on-board sensors are being developed and implemented over the course of one or more decades
D.) There are a significant number of derailments that could be prevented by the kinds of problems that on-board sensors could detect.
I'ma make a separate post in another thread about the economics of installing on-board sensors to prevent accidents. Suffice it to say, I think your wrong about (B), (C), and (D).
The whole is greater than the sum of the parts. RRs are currently having a nice "going out of business sale". PSR is really just a way to squeeze the last drops from declining carload franchise. Are there any leaders out there with any vision for this industry?
Railroad market share has been decling since the 1920's. Dieselization didn't reverse that trend, deregulation didn't reverse that trend, PTC hasn't reversed that trend, and ECP brakes won't either unless they can vastly improve the efficiency of basic railroad tasks, especially switching. Which, as currently envisioned, they don't do.
On the other hand, deregulation has led to an industry that is profitable and greatly slowed down the rate at which the industry is disappearing. So one should be hesitant to start regulating the industry "for its own good."
Dan
SD60MAC9500 The stopping distance is a bonus of ECP yet imagine with improved braking how many grade crossing incidents could potentially be avoided? Or even low/medium speed rail collisions?
dpeltierUnlike service braking distances, the difference in emergency braking distances between ECP and state-of-the-art-practice conventional air brakes is quite small.
I know I've seen info on how long it takes for an emergency application to travel the length of the train, but I can't find it at the moment.
It's important to note that unlike a service brake application, where all of the air from the brake line vents at the controlling locomotive, with an emergency application, each car also dumps the brake line as it senses the rapid drop in pressure. Thus the emergency application is telegraphed the length of the train quite quickly.
ECP may apply all the brakes in emergency at the same time, but that time difference will be negligible when the physics of the operation is considered.
Modern EOTs can also make an emergency application, so it's happening from both ends. I can't speak to how DPUs work in that regard.
After that, it's all coefficient of friction. The train will stop when it's good and ready.
tree68 dpeltier Unlike service braking distances, the difference in emergency braking distances between ECP and state-of-the-art-practice conventional air brakes is quite small. I know I've seen info on how long it takes for an emergency application to travel the length of the train, but I can't find it at the moment. It's important to note that unlike a service brake application, where all of the air from the brake line vents at the controlling locomotive, with an emergency application, each car also dumps the brake line as it senses the rapid drop in pressure. Thus the emergency application is telegraphed the length of the train quite quickly. ECP may apply all the brakes in emergency at the same time, but that time difference will be negligible when the physics of the operation is considered. Modern EOTs can also make an emergency application, so it's happening from both ends. I can't speak to how DPUs work in that regard. After that, it's all coefficient of friction. The train will stop when it's good and ready.
dpeltier Unlike service braking distances, the difference in emergency braking distances between ECP and state-of-the-art-practice conventional air brakes is quite small.
I have read that normal air brakes propagte at the speed of sound, which I think is supposed to be somewhere near 768 MPH. ECP is supposed to be near the speed of Light or 186000 MPS.
When all is applied, there are still thousands of tons of mass to be stopped with the coefficient of friction beween steel wheels and steel rail.
Never too old to have a happy childhood!
BaltACDI have read that normal air brakes propagte at the speed of sound, which I think is supposed to be somewhere near 768 MPH. ECP is supposed to be near the speed of Light or 186000 MPS.
Agreed. That would mean that an emergency application initiated only from the head end would take about eleven and a half seconds to travel the length of the train.
Figure half that for a simultaneous EOT dump, and then it depends on whether DPUs add any advantage.
An emergency application propogates at about 950 ft per second. The service rate is slower around 250 ft per second. If the lead consist is placed into emergency, the DP consist(s) will also go into emergency. Some engines are equipped to dump the EOT when the engineer places the automatic into emergency. Instructions are to toggle the EOT emergency switch anyway when placing the handle into the emergency position.
Jeff
jeffhergertJeff
Thanks for the clarification.
BaltACD ECP is supposed to be near the speed of Light or 186000 MPS.
ECP is supposed to be near the speed of Light or 186000 MPS.
Velocity of propagation along a wire is often significantly less that the speed of light in a vacuum. My finger in the air guess for ECP control lines would be 70% of the speed of light in a vacuum. Having said that, there will likely be more of a delay in the electically controlled valves opening than it take the signal to reach the end of the train.
1. Apologize for tghe serious eror in the casec of Megantic. Slow cleak. Would not have triggered ECB in any case.
2. Speed vin wire significantly less than light? In any case, far, far faster than air-pre3ssure change in train-line.
daveklepper2. Speed vin wire significantly less than light? In any case, far, far faster than air-pressure change in train-line.
For our purposes, signal through the wire will be virtually instantaneous. As Balt notes, though, it's still air from the valve to the brake cylinders, and from that point, Newton is still valid.
tree68 As Balt notes, though, it's still air from the valve to the brake cylinders, and from that point...
As Balt notes, though, it's still air from the valve to the brake cylinders, and from that point...
The point being made is that while ECP can improve train handling and allows for a faster response, it will still take a fair amount of time to stop 200 cars.
dpeltierMaybe? I kind of doubt it. Are cars really designed for the purpose of survive emergency slack run-in? They're designed to handle normal in-train forces, many of which occur without the automatic brakes being engaged at all, and forces experienced during switching and coupling activities. For the structural elements of the car (as opposed to the draft gear), surviving over speed coupling events (i.e. 6+ MPH collisions) may be limiting factor.
All true, but not immutable. High buff/draft forces come from having locomotives only on the head end. DPU changes the game - if you do it right. Also worth noting Roadrailers only good for 400,000# buff/draft.
Building for 6 mph collisions probably doesn' require 800,000# buff/draft - sort of like slack run in, no?
dpeltierIn what context exactly? The reservoirs still have to be charged from the train line.
Trainline current fed throttled though locomotive brake valve. Wide open trainline at higher pressure charges reservoirs much faster. Once you get rid of co-mingled power and control signal, you can do this.
dpeltierOn the mainline, most contexts requiring restricted speed are either a.) solvable by the more-advanced train-control systems that are in the works, thanks to PTC, or b.) protecting a potential track defect such as a broken rail, where there is good reason to limit speeds anyways. In yards, 80-90% of all tracks are limited to 10 MPH by turnout size and track condition. And many movements within the yard don't have air cut in except on a few cars on the head end. (If braking performance was limiting yard capacity, we could start by using more of the existing brakes.)
All true. Not immutable. Clearly better yard track condition would be needed. Take a look at Machen yard in Hamburg Germany. They wheel out of the class yard on signals on to the main. Chicken and egg. Lousy yard tracks because you can't go fast or can't go fast because of lousy track?
dpeltierBecause why? See #2 and #3. For a setout in particular, I'm not seeing any savings. For a pickup, you still need to charge the air on the cars you're picking up, and you still need to do at least a minimal inspection to ensure they're all on the rail. Parking brakes that could be set and released from the head end - which is something that has been discussed on this forum - would be convenient. Like on-board sensors, those don't necessarily require ECP brakes, although IF the EC line is designed for it, this feature might be able to take advantage of it.
You can bottle the air. Have potential for automating hand brake. You don't have to start from "empty". You can't bottle the air now because you are dependent on the trainline for your control signal.
dpeltierThis requires assuming many things that are unknown, such as: A.) The EC line supplies power to these sensors and can make use of data from them B.) On-board sensors can be developed that work reliably with acceptable installation and maintenance costs C.) Such sensors do a better job of preventing derailments than wayside detectors + periodic car inspection - allowing for the fact that wayside detector technology is also continuing to improve while the on-board sensors are being developed and implemented over the course of one or more decades D.) There are a significant number of derailments that could be prevented by the kinds of problems that on-board sensors could detect.
No show stoppers anywhere here. Lots of robust technology to choose from.
Stuck truck and hunting derailments are pretty rare, but not insignificant since they most often happen at speed. No wayside detection exists.
Euclid Does ECP make a full emergency application to all cars simultaneously if the train breaks in two? If so, is this activated by the parting of the electric line? If so, how does this work in detail? If the electric line parts, there is no power from the parting location to the end of the train. So what communicates to the unpowered cars and provides the power for them to send their emergency reservoir air into their brake cylinders?
So, existing systems have two parts to brake valve. An emergency portion and a service portion. As far as I know, existing ECP trials have only included service portion. Emergency from break in two, would still trigger emergency braking to "old fashioned" way.
I could see a "both/and" solution. Trainline rapidly to zero? Emergency braking and put the "word" out on the data trainline.
It's important to remember that a lot of air brake technology requires the controls having to "tiptoe" around stability issues. The whole thing has been built and calibrated to:
a) react as fast as possible
while
b) not reacting to transients.
It is the rate of change of pressure that determines emergency versus service braking. The control valves are damped not to react to transients that come from pressure waves bouncing around and reflecting off surfaces in the trainline.
The feed valve on the locomotive is regulated not to allow high flow rates in order to keep things stable. Too fast and you could trigger valves in the train to do all sorts of nasty things, like UDE and stuck brakes.
It's an outdated system. While pneumatic controls were pretty common in the analog days (Baldwin air throttles, anyone?) they all faded away by the 1970s. "Westinghouse" air brakes might be the last...
Erik_Mag BaltACD ECP is supposed to be near the speed of Light or 186000 MPS. Velocity of propagation along a wire is often significantly less that the speed of light in a vacuum. My finger in the air guess for ECP control lines would be 70% of the speed of light in a vacuum. Having said that, there will likely be more of a delay in the electically controlled valves opening than it take the signal to reach the end of the train.
Damn. So, 0.00002 seconds for the signal to get to the EOT!
I would think an ECP system could build brake cylinder pressure faster than current system, because you're not trying to do the dance to match brake pipe pressure. Transients on the brake cylinder pressure side of things that you'd get from dumping air in fast would likely give the control valve fits.
It would still take longer than 0.00002 seconds, though!
BaltACDWhen all is applied, there are still thousands of tons of mass to be stopped with the coefficient of friction beween steel wheels and steel rail.
Gonna send you back to Physics class, too! Maximum braking force is coeff of friction x mass of car. Also, F=ma.
coeff of friction x m = F = m x a. m cancels out. max decelleration = coeff of friction. Doesn't matter if 1 lb or 10,000 tons.
oltmannd Euclid Does ECP make a full emergency application to all cars simultaneously if the train breaks in two? If so, is this activated by the parting of the electric line? If so, how does this work in detail? If the electric line parts, there is no power from the parting location to the end of the train. So what communicates to the unpowered cars and provides the power for them to send their emergency reservoir air into their brake cylinders? So, existing systems have two parts to brake valve. An emergency portion and a service portion. As far as I know, existing ECP trials have only included service portion. Emergency from break in two, would still trigger emergency braking to "old fashioned" way. I could see a "both/and" solution. Trainline rapidly to zero? Emergency braking and put the "word" out on the data trainline.
EuclidSay you have a 200-car train with ECP. The 200 car valves open simultaneously (for all practical purpose). Then it takes just a split second for all 200 car brakes to fully set simultaneously with maximum force.
It doesn't take long for the brakes to apply, but it's not instantaneous. Air is still a fluid, flowing through pipes and hoses. And there is the mechanical portion of the system.
Even if it were instantaneous, there's Newton.
tree68 Euclid Say you have a 200-car train with ECP. The 200 car valves open simultaneously (for all practical purpose). Then it takes just a split second for all 200 car brakes to fully set simultaneously with maximum force. It doesn't take long for the brakes to apply, but it's not instantaneous. Air is still a fluid, flowing through pipes and hoses. And there is the mechanical portion of the system. Even if it were instantaneous, there's Newton.
Euclid Say you have a 200-car train with ECP. The 200 car valves open simultaneously (for all practical purpose). Then it takes just a split second for all 200 car brakes to fully set simultaneously with maximum force.
Damn that Newton - Give him some figs.
Isn't it amazing how quickly a bit or byte can be stopped versus over 100 tons of rail car assembled in 15K ton, 20K ton, 30K ton trains.
oltmannd I would think an ECP system could build brake cylinder pressure faster than current system, because you're not trying to do the dance to match brake pipe pressure. Transients on the brake cylinder pressure side of things that you'd get from dumping air in fast would likely give the control valve fits. It would still take longer than 0.00002 seconds, though!
That's exactly my point and was having a little fun with the difference in velocity of light in a vacuum as opposed to a cable. This has been very relevant in the work I've doing the last couple of years.
I've been wondering if installing the equivalent of a dynamic brake on each car migh be an even better way to go with the air brakes kept as back-ups. These could be set up to do a maximum power point tracking which would continuously try to find the braking effort that gives maximum electrical power output from the generators. One advantage is further reduction in brake wear and presumably less heating of the journal bearings. This, of course, is even more blue sky than ECP, but potenially could added on to cars equipped for ECP. Biggest problem is where to mount the generators on a three piece truck.
Generators are in pairs, hinged on slide pins like those for disc-brake calipers from the truck bolster, with a central pulley (probably for the Gates belts proposed for boosters in the '80s). There need to be Weller tensioners on both the top and bottom of the loop, otherwise the car will not 'set up' properly in one direction.
Obviously (to me) this is also the only practical solution to 'autonomous' drive. My suspicion is that both applications would have to be marketed and sold synergistically to make the idea worth anything practically.
oltmannd dpeltier Maybe? I kind of doubt it. Are cars really designed for the purpose of survive emergency slack run-in? They're designed to handle normal in-train forces, many of which occur without the automatic brakes being engaged at all, and forces experienced during switching and coupling activities. For the structural elements of the car (as opposed to the draft gear), surviving over speed coupling events (i.e. 6+ MPH collisions) may be limiting factor. All true, but not immutable. High buff/draft forces come from having locomotives only on the head end. DPU changes the game - if you do it right. Also worth noting Roadrailers only good for 400,000# buff/draft. Building for 6 mph collisions probably doesn' require 800,000# buff/draft - sort of like slack run in, no?
dpeltier Maybe? I kind of doubt it. Are cars really designed for the purpose of survive emergency slack run-in? They're designed to handle normal in-train forces, many of which occur without the automatic brakes being engaged at all, and forces experienced during switching and coupling activities. For the structural elements of the car (as opposed to the draft gear), surviving over speed coupling events (i.e. 6+ MPH collisions) may be limiting factor.
I don't follow you. The question was whether ECP brakes would let you design lighter freight cars. I still think that humping, kicking, and moving cars around in the yard with no air cut in will quickly put a lower limit on how much you can reduce the strength and tare weight of a car with ECP brakes. Does a Roadrailer have lower buff strength limits because it operates in a low-slack train, or because it never goes through the abuse of a classification yard?
dpeltier On the mainline, most contexts requiring restricted speed are either a.) solvable by the more-advanced train-control systems that are in the works, thanks to PTC, or b.) protecting a potential track defect such as a broken rail, where there is good reason to limit speeds anyways. In yards, 80-90% of all tracks are limited to 10 MPH by turnout size and track condition. And many movements within the yard don't have air cut in except on a few cars on the head end. (If braking performance was limiting yard capacity, we could start by using more of the existing brakes.) All true. Not immutable. Clearly better yard track condition would be needed. Take a look at Machen yard in Hamburg Germany. They wheel out of the class yard on signals on to the main. Chicken and egg. Lousy yard tracks because you can't go fast or can't go fast because of lousy track?
dpeltier On the mainline, most contexts requiring restricted speed are either a.) solvable by the more-advanced train-control systems that are in the works, thanks to PTC, or b.) protecting a potential track defect such as a broken rail, where there is good reason to limit speeds anyways. In yards, 80-90% of all tracks are limited to 10 MPH by turnout size and track condition. And many movements within the yard don't have air cut in except on a few cars on the head end. (If braking performance was limiting yard capacity, we could start by using more of the existing brakes.)
Track condition is only one of the reasons I mentioned for why ECP brakes don't hold great promise for improving operating efficiency in half-the-range-of-vision operations. In yards, turnouts sizes and curvature (including reverse curvature) are much more intractable.
I watched a YouTube video showing some operations in Maschen yard. They didn't show anything that appeared to be going much faster than 10 MPH, except for things passing by on the mainline. Looking at aerials of the track layouts, I can see why.
At the hump yard near my office they increased track speeds to 20 MPH on a few key tracks where the geometry supports it. For arriving trains it probably won't make much difference due to concerns about sight distance. On the other hand, departing trains can speed up as soon as the head end is out on the mainline and the rest of the train is on the higher-speed tracks. For other cuts moving around using an RCO without air, higher speeds are not going to happen in the near future.
dpeltier Because why? See #2 and #3. For a setout in particular, I'm not seeing any savings. For a pickup, you still need to charge the air on the cars you're picking up, and you still need to do at least a minimal inspection to ensure they're all on the rail. Parking brakes that could be set and released from the head end - which is something that has been discussed on this forum - would be convenient. Like on-board sensors, those don't necessarily require ECP brakes, although IF the EC line is designed for it, this feature might be able to take advantage of it. You can bottle the air. Have potential for automating hand brake. You don't have to start from "empty". You can't bottle the air now because you are dependent on the trainline for your control signal.
dpeltier Because why? See #2 and #3. For a setout in particular, I'm not seeing any savings. For a pickup, you still need to charge the air on the cars you're picking up, and you still need to do at least a minimal inspection to ensure they're all on the rail. Parking brakes that could be set and released from the head end - which is something that has been discussed on this forum - would be convenient. Like on-board sensors, those don't necessarily require ECP brakes, although IF the EC line is designed for it, this feature might be able to take advantage of it.
Well, as I understand it, the only reason you can't bottle the air is because it can lead to unintended brake releases. And that's only a problem because people still can't be relied on to set adequate hand brakes. A way to easily set parking brakes on however many cars you want would solve that problem, too.
dpeltier This requires assuming many things that are unknown, such as: A.) The EC line supplies power to these sensors and can make use of data from them B.) On-board sensors can be developed that work reliably with acceptable installation and maintenance costs C.) Such sensors do a better job of preventing derailments than wayside detectors + periodic car inspection - allowing for the fact that wayside detector technology is also continuing to improve while the on-board sensors are being developed and implemented over the course of one or more decades D.) There are a significant number of derailments that could be prevented by the kinds of problems that on-board sensors could detect. No show stoppers anywhere here. Lots of robust technology to choose from.
dpeltier This requires assuming many things that are unknown, such as: A.) The EC line supplies power to these sensors and can make use of data from them B.) On-board sensors can be developed that work reliably with acceptable installation and maintenance costs C.) Such sensors do a better job of preventing derailments than wayside detectors + periodic car inspection - allowing for the fact that wayside detector technology is also continuing to improve while the on-board sensors are being developed and implemented over the course of one or more decades D.) There are a significant number of derailments that could be prevented by the kinds of problems that on-board sensors could detect.
In the thread about on-board sensors I point out that if someone developed an on-board wheel bearing temp sensor which had a 20-year service life and would prevent 80% of all wheel-bearing derailments while creating no false positives, it would have to have a lifecycle cost (manufacturer, installation, and 20 years of maintenance) of around $60 just to break even. (Not including development costs or cost of capital.)
The tire pressure sensors in my car cost around $100 to install and have a service life of only 5-10 years. So their lifecycle cost is at least 2-4 times what it would take to break even on an on-board hot box sensor. If there is robust technology out there like you describe, how come they're not using it for tire pressure sensors?
Quoting from https://railroads.dot.gov/sites/fra.dot.gov/files/2022-05/Effectiveness%20of%20Wayside%20Detector%20Tech.pdf
"As of August 2013, AAR reported a total of 171 WILDs, 78 THDs, 27 TPDs, and 21 TADs installed and providing data for InteRRIS® and EHMS purposes. These detectors are spread over the North American railroad system that includes U.S., Canada, and Mexico."
"THD" in that sentence refers to a Truck Hunting Detector, which is a wayside device to detect trucks with incipient signs of hunting.
Truck hunting is actually something where wayside detectors and / or appropriate periodic inspection should be able to address the problem. It results primarily from running gear wearing out over time, in a way that can be measured and tracked non-destructively. It's a much easier thing to catch with a limited number of detection sites than something like a hot box or broken axle, which can happen suddenly without warning. Trends in the data for a given car may also give private car owners a chance to "home shop" the car for repairs before it becomes condemnable - which can be cheaper than paying AAR repair rates.
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